Rotary pumps and motors



Jan. 9, 1962 c. s. PRENDERGAST 3,0 7

ROTARY PUMPS AND MOTORS Filed Aug. 21, 1959 4 Sheets-Sheet 1 F/6.2."-/ 5loc K F H Pain 12 22;

Jan. 9, 1962 C. S. PRENDERGAST ROTARY PUMPS AND MOTORS Filed Aug. 21,1959 F/GEB.

4 Sheets-Sheet 2 Jan. 9, 1962 c. s. PRENDERGAST 3,01

ROTARY PUMPS AND MOTORS 4 Sheets-Sheet 3 Filed Aug. 21, 1959 FIGS.

corr v PR5 ERGAST,

B 5 5 L Attorney //v VE/VTOR CHARLL'S Jan. 9, 1962 c. s. PRENDERGAST3,016,017

ROTARY PUMPS AND MOTORS Filed Aug. 21, 1959 4 Sheets-Sheet 4 3,3 F/ G 8.7 28b 33a WIN/[A1709 C/MRL saorr 8o P/mvomawr,

Atlorne United States Patent Oflice 3,015,017 Patented Jan. 9, 19623,016,017 ROTARY PUMPS AND MOTORS Charles Scott Prendergast,Shoreham-by-Sea, England, assignor to Brakeshoe International, S.A.,Geneva, Switzerland, a corporation of Switzerland Filed Aug. 21, 1959,Ser. No. 835,301 Claims priority, application Great Britain Dec. 23,1958 Claims. (Cl. 1034) This invention relates to pumps and motors ofthe kind having three rotors concentrically mounted and rotatable with acentral shaft, a similar number of bored stators surrounding said rotorsat least the centre one of which stators is or may be set eccentricallyin relation to the axis of the shaft, and vanes slidable in radialgrooves in each rotor having an eccentric stator.

An object of the invention is to eliminate the previous necessity inmachines of this kind for separating or partitioning plates or likemembers between the respective fluid chambers.

According to the invention and to the attainment of this object Iprovide a pump or motor of the aforesaid kind in which the diameter ofthe centre rotor differs from that of the two end rotors and the productof the 7 diameter and axial width of either of the two end rotors isapproximately equal to half the product of the diameter and axial widthof the centre rotor. This arrangement provides sealing surfaces betweenthe respective fluid chambers without the necessity for separating orpartitioning plates or equivalent members.

The invention is applicable to a pump or motor in which the bores of thestators for all three rotors are eccentric to the shaft axis and inwhich all three rotors are equipped with vanes slidable in radialgrooves there- However, the invention is also applicable to a pump ormotor in which the bore of the centre stator alone is eccentric to theshaft axis and its rotor is equipped with vanes slidable in radialgrooves therein, while the bore of each of the end stators is concentricto the shaft axis and carries two abutments (which may be radiallyslidable) on approximately the same centre line as the eccentricity ofthe centre stator, these abutments making sealing contact with theunbroken periphery of the pertaining rotor.

In either case the pump or motor may be so constructed that theeccentricity of the bore of the centre stator is capable of being variedat will as in accordance with my patent application Ser. No. 710,573,now PatentNo. 2,972,953.

In order that the invention may be better understood two embodimentsthereof as applied to'pumps are illustrated by way of example on theaccompanying drawings to which reference is now made.

FIG. 1 is a longitudinal section on II of FIG. 2.

FIG. 2 is a transverse section on II-II of FIG. 1.

FIG. 3 is a transverse section on IIIIII of FIG.

FIG. 4 is a transverse section on IV-IV of FIG.

FIG. 5 is a longitudinal section on V-V of HG.

FIG. 6 is a transverse section on VI-VI of FIG. FIG. 7 is a transversesection on VII-VII of'FiG,

FIG. 8 is a transverse section on VIII-VIII of FIG.

Referring" first to FIGURES 1 to 4, a shaft 1 is carried inball-bearings 2 and 3 mounted in end housings 4 and 5. Keyed to theshaft but free to slide axially on it is"a rotor 6, and rigidly andconcentrically mounted on exby that rotors axial width is equal to halfthe product of the diameter and the axial width of the rotor 6.

Each of the three rotors 6, 7, 8 is provided with eight pairs ofequidistant grooves 6a, 7a, 8a respectively, these grooves being ofequal depth and extending inwardly from the rotor periphery and theirbottoms being connected by ducts 6b, 7b, 8b respectively to saidperiphery between adjacent pairs of grooves. The construction of eachrotor is in accordance with my Patent No. 2,928,350.

Surrounding the rotor 6 is an adjustable stator 9, approximately thesame axial width as this rotor and having a circular bore which issubstantially greater in diameter than the rotor but substantially lessthan a circle inscribed at the bottoms of the grooves 7a and 8a;surrounding the rotors 7 and 8 are stators 12 and 13 of approximatelythe same axial width as these rotors and having circular bores which aresubstantially greater in diameter than the rotors. The describedarrangement of the rotors and their stators forms sealing surfacesbetween the respective fluid chambers without the necessity forseparating or partitioning plates thereby simplifying the construction.

The adjustable stator 9 is carried in slides 10a and 10b in an outermember 10 and has freedom to move transversely in these slides inrelation to the rotor 6 from a position where the centre of the statorbore is a predetermined distance on one side of the shaft axis to aposition in which it is a predetermined distance on the other side ofthe shaft axis. Sixteen vanes 11, approximately the same axial width asthe rotor 6, are free to slide radially in the grooves 6a; they maintaincontact with the bore of the stator 9 by centrifugal force when therotor is rotated (with or without the aid of springs). Chambers 9a and9b extend radially outwards from the bore of the stator 9 and areseparated by equal unbroken portions 90 of the stator bore, each ofthese portions havin a reater angular length'than the an ular distance ag a Chamber 9b is a non-pressure chamber and is connected tensions atopposite endsof the rotor 6 are two other '6. In fact'the dia'meterofthe rotor,7 'or 8 multiplied by a duct 9e to a non-pressure port 10dconnected to the fluid reservoir. f

The stators 12 and 13 are fixed radially in relation to the rotors 7 and8, their bores having a predetermined and identical eccentricity inrelation to the shaft axis on the same transverse plane as that on whichthe adjustable stator 9 moves. Sixteen vanes 14 and sixteen vanes 15,approximately the same axial width as the rotors 7 and 8, are free toslide radially in the grooves 7a and 8a respectively; these vanesmaintain contact with the bores of the stators 12 and 13 by centrifugalforce when the rotors are rotated (with or without the aid of springs).Chambers 12a, 12b and 13a, 13b extend radially outwards from the boresof the stators 12 and 13 respectively, the chambers in each stator beingseparated by equal unbroken portions of the stator bore or 130, each ofthese portions having a greater angular length than the angular distancebetween adjacent pairs of the vanes. The chambers 12a, 12b, and 13a,13b, 'are on transverse planes at right angles to the plane in which theadjustable stator 9 moves; The chambers 12a and 13a are pressure to theshaft-axis: Duct 17 connects'to the inletpor't 10a in. the outer member16.

Duct 16 connects to the output port When the described pump is adjustedfor full flow, the eccentricity of the adjustable stator 9 is at itsmaximum and is at 180 to the eccentricities of the stators 12 and 13.There is then a gap between the adjustable stator and the outer member10. Small diameter holes 9 and 9g connect this gap to the pressurechamber 9a and the non-pressure chamber 9b, thus creating a fluidpressure at this side of the adjustable stator 9 which holds it in thefull flow position. When the adjustable stator is in the full flowposition and the rotors are rotated, the displacement thus createdcauses fluid to enter through the ports d and 10a and to be expelledthrough the utlet port 100.

For the purpose of adjusting the stator 9 at will the outer member 10 isequipped with an adjusting screw 18 and an adjusting nut 19, which areretained in position by a retaining plate 20. By rotating the adjustingnut, the adjusting screw can be moved inwards against the adjustablestator 9 forcing it to move towards the other side of the outer member10. 7

When the adjustable stator 9 is moved towards the concentric positionthe displacement created between it and the rotor 6 is reduced andbecomes zero when the stator reaches the concentric position, so that atthis point the total displacement of the pump is created between the endrotors 7 and 8 and the end stators 12 and j 13. If the adjustable stator9 is moved farther to become eccentric with the shaft axis in the samedirection as the eccentricities of the stators 12 and 13, thedisplacement created between it and the rotor 6 absorbs a proportion ofthe fluid displaced by the rotors 7 and 8 and this fluid is expelledthrough the non-pressure port 10d back to the reservoir. Under theseconditions the rotor 6 is being driven by pressure fluid displaced bythe rotors 7 and 8 and ,the energy represented by this displacement isbeing returned to the shaft 1. By moving the adjustable stator 9 farenough in this direction all the fluid displacement by the rotors 7 and8 is returned to the reservoir through the nonpressure port 10d andapart from volumetric and other losses no energy is absorbed v by thepump.

Referring now to FIGS. 5 to 8, a shaft 21 is carried in ball-bearings 22and 23 mounted in end housings 24 and 25. Keyed to the shaft but free toslide axially on it is a vane-bearing rotor 26 and rigidly andconcentrically mounted on extensions at opposite ends of the rotor 26are two pressure re-action rotors 27 and 28, all three rotors formingone rotatable unit concentric with the axis a grooves are connected byducts 26b to said periphery between adjacent pairs of grooves. Theconstruction of the rotor 26 is in accordance with my Patent No.2,928,350. l

Surrounding the. rotor 26 an adjustable stator 29, approximately thesame axial width as the rotor'and having a circularbore which issubstantially greaterin" diameter than the rotor but substantially lessthanfthe di-' ameter of either of the pressure re-action rotors27, 28;

surrounding the" pressure re-action rotors '27, 28 are r fixedstators32, 33 .r'espectively, approximately the same :axi'a'l width as therotors and having circular bores which 1 are concentric withand'slightly greater in diameter than the rotors 27, 28. Thisarrangement Be he rotorsla nd' their stators forms sealing surfacesbetween the respective fluid. chambers withoutthe necessity forseparating or partitioning "plates. :I V

. nectthis gap to the outletchamb'e'r 29a and the inlet by centrifugalforce when the rotor is rotated (with or Without the aid of springs).Chambers 29aand 29b extend radially outwards from the bore of the stator29 and are separated by equal unbroken portions 29c of the stator bore,each of these unbroken portions having a greater angular length than theangular distance between adjacent pairs of vanes 31-. The chambers 29aand 29b are situated on a transverse plane at right angles to that onwhich the adjustable stator 29 moves. Chamber 29a is the outlet chamberand is connected directly to the pump outlet port 300 in the outermember 30. Chamber 29b is the inlet chamber and is connected directly tothe inlet port 30d. 7

Each of the fixed stators 32 and 33 has two radial grooves 32a and 33arespectively, which extend radially outwards from the bores of thestators. Two abutments 34 and two abutments 35 are free to slideradially in the grooves 32a and 33a respectively, and these abutmentsare constrained to make sealing contact with the pressure reactionrotors 27 and 28 by hydraulic pressure (with or without the aid ofsprings). Abutments 34 and 35 are situated on a centre line parallel tothe slides 30a and 30b in which the adjustable stator 29 moves. Theannular spaces between the pressure reaction rotors 27 and 28 and thefixed stators 32 and 33 are divided into four chambers 27a, 27b and 28a,28b by the abutments 34 and 35. Chambers 27a and 28a are connected byducting (not shown) to the outlet chamber 29a and are situated at 180 toit. Chambers 27b and 28b are connected by ducting (not shown) to theinlet chamber 2% and are situated at 180 to it.

Owing to the stated dimensional relationship between thepressurereaction rotors 27 and 28 and the vane-bearing rotor 26, the sumof the cross-sectional areasof the rotors 27 and 28 is equal to thecross-sectional area of the rotor 26. As the chambers 27a, and 28a'areat 180 tothe outlet chamber 29a and are hydraulically connected to it,any hydraulic pressure developed in the output chamber 29a is balancedby the hydraulic pressures in the chambers 27a and 28a thus tending toeliminate bearing loading due to internal hydraulic pressure.

When the rotor 26 is rotated fluid. is displaced between it and theadjustable stator 29 and by reason of this displacement fluid'entersthrough the inlet port 30d and is expelled through the outlet port 300.The volume of fluid displaced can be varied from zero to maximum byadjusting the position of the adjustable stator 29 between the positionof concentricity with the shaft axis and the position of maximumeccentricity withjthe shaft axis.

When the pump is adjusted for full flow, the eccentricity of theadjustable stator 29 is at its maximum. There is then a gap between theadjustable'st'ator and the outer member. Small diameter holesj29j and29g conchamber. "2%. thus creating a fluid pressure at. this side oftheadjustable stator 29 whichh'olds' it in the full flow position; onthe opposite side-tor the outer member 30 are an adjusting screw 38 andah adjusting nut 39 ingit-to move towardslthe concentric position. '1 ai "It will be understood yifthos jsliilled inj'ith'e art that a althoughI- have described jlation: to pumps it'isapplicableftoftheconstrictionof 7 jhydraulic motors. Furtherl many conseueagnar :det'ails'fwhich' are retained in position -by afretaining plate 40.

By rotating'the adjusting nut the ,adjusting sCIFW can be moved inwardsagainst the adjustable stator. 29, forcthe invention in detailin remaybe modified within the scope of the invention; for instance means otherthan described may be provided for adjusting the eccentricity of thecentre stator.

I claim:

1. A pump or motor comprising end housings; a shaft journalled forrotation in said end housings; three rotors arranged side-by-side withtheir adjacent surfaces in sealing contact, mounted on and rotatablewith said shaft; three bored stators each surrounding one of said rotorsto form part annular fluid spaces of equal angular length therewith, atleast the bore of the center stator being eccentric to the axis of saidshaft; a plurality of vanes equally spaced and slidable in radialgrooves formed in at least the center rotor to provide with its stator aseries of fluid displacement chambers; fluid inlet and outlet chambersof equal angular length on opposite sides of the plane of eccentricityof at least the center stator bore, lands of equal angular lengthsituated on the circumference of the stator bore separating said inletand outlet chambers, each land having an angular length at least equalto the angular distance between adjacent rotor vanes; ducting connectingthe part annular fluid space on each side of the plane of eccentricityof the center stator to the part annular fluid spaces contained by theend rotors and their stators on the opposite side of said plane; thediameter of the center rotor differing from that of the two end rotorsin sealing contact with it, thereby affording sealing surfaces betweenthe respective part annular fluid spaces contained by the three rotorsand stators without partitioning members between the rotors, and theproduct of the diameter and the axial width of each of the end rotorsbeing substantially equal to half the product of the diameter and theaxial width of the center rotor thereby insuring that the area underradial hydraulic pressure of the center rotor is approximately equal andopposite to the sum of the areas under hydraulic radial pressure of thetwo end rotors.

2. A pump or motor as set forth in claim 1, including means for varyingat will the eccentricity of the bore of the centre stator.

3. A pump or motor comprising end housings; a shaft journalled forrotation in said end housings; three rotors arranged, side-by-side, withtheir adjacent surfaces in sealing contact, mounted on said shaft androtatable with said shaft; three bored stators each surrounding one ofsaid rotors to form part annular fluid spaces of approximately equalangular length therewith, the bores of the stators being eccentric tothe axis of said shaft; the eccentricities of the end stators beingequal to one another and fixed on coincidental radii on the same planeof eccentricity as the central stator; a plurality of vanes equallyspaced and slidable in radial grooves formed in each of said rotors toprovide a series of displacement chambers with the bores of theirstators; fluid inlet and outlet chambers of equal angular length onopposite sides of the plane of eccentricity of each stator bore, landssituated on the circumference of each stator bore separating said inletand outlet chambers of each stator, each land having an angular lengthat least equal to the angular distance between adjacent rotor vanes,ducting connecting the part annular fluid space on each side of theplane of eccentricity of the center stator to the part annular fluidspaces contained by the end rotors and their stators on the oppositeside'of said plane; the diameter of the center rotor differing from thatof the two end rotors in sealing contact with it, thereby affordingsealing surfaces between the respective part annular fluid spacescontained by the three rotors and their stators without partitioningmembers between the rotors, and the product of the diameter and theaxial width of each end rotor being substantially equal to half theproduct of the diameter and the axial width of the center rotor therebyensuring that the area under radial hydraulic pressure of the centerrotor is approximately equal and opposite to the sum of the areas underhydraulic radial pressure of the two end rotors.

4. A pump or motor as set forth in claim 3, including means for varyingat will the eccentricity of the bore of the center stator on the sameplane as the fixed eccentricities of the end stators.

5. A pump or motor comprising end housings; a shaft journalled forrotation in said end housings; three rotors arranged side-by-side withtheir adjacent surfaces in sealing contact, mounted on said shaft androtatable with said shaft; three bored stators each surrounding one ofsaid rotors to form part annular spaces of equal angular lengththerewith, the bore of the center stator being eccentric to the axis ofsaid shaft and the bores of the end stators being concentric to saidaxis; a plurality of vanes equally spaced and slidable in radial groovesin the center rotor to form with its stator a series of displacementchambers; two abutments slidable in radial grooves formed in theconcentric bore of each end stator and bearing on the pertaining rotoron approximately the same plane as the plane of eccentricity of thecenter stator bore with the shaft axis; fluid inlet and outlet chambersof equfl angular length on opposite sides of the plane of eccentricityof the center stator bore, lands of equal angular length situated on thecircumference of the stator bore separating said inlet and outletchambers, the angular length of each land being at least equal to theangular distance between adjacent rotor vanes; ducting connecting thepart annular fluid space on each side of the plane of eccentricity ofthe center stator to the part annular fluid spaces contained by the endrotors and their stators on the opposite side of said plane; thediameter of the center rotor differing from that of the end rotors insealing contact with it, thereby affording sealing surfaces between therespective part annular fluid spaces contained by the three rotors andstators without partitioning members between the rotors, and the productof the diameter and the axial width of each of the end rotors beingsubstantially equal to half the product of the diameter and the axialwidth of the center rotor thereby ensuring that the area under radialhydraulic pressure of the center rotor is approximately equal andopposite to the sum of the areas under hydraulic radial pressure of thetwo end rotors.

6. A pump or motor as set forth in claim 5, including means for varyingat will the eccentricity of the bore of the centre stator.

References Cited in the file of this patent UNITED STATES PATENTS722,560 Buckingham Mar. 10, 1903 1,927,799 Mann Sept. 19, 1933 2,013,397Balsigcr Sept. 3, 1935 2,358,275 Hess Sept. 12, 1944 2,368,789 TuckerFeb. 6, 1945 2,513,446 Brown July 4, 1950 2,754,762 Prendergast July 17,1956 2,885,960 Deschamps May 12, 1959 FOREIGN PATENTS 743,088 GreatBritain Ian. 11, 1956 819,195 Germany Oct. 31, 1951

